Internal combustion engine

Abstract

The invention relates to an internal combustion engine with a laser ignition device (1), Q-switched, pumped solid-state laser with a pulsed pumped light source (30), a solid laser crystal (2), enclosed in a resonator, a Q-switch (4), for increasing the power density, at least one output mirror (6) and a focussing device (7), by means of which the laser beam (26) may be focussed in a combustion chamber.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to an internal combustion engine with a laser ignition device, comprising a Q-switched, pumped solid-state laser with a pulsed pumped light source, a solid laser crystal embedded in a resonator, a Q-switch for increasing the power density, at least one output mirror and a focusing device, by means of which the laser beam may be focused in a combustion chamber.[0003]The invention further relates to a Q-switched, pumped solid state laser, especially for a laser ignition device of an internal combustion engine, comprising a pulsed pumped light source formed by pump diodes, a solid laser crystal embedded in a resonator, a Q-switch for increasing the power density, at least one output mirror and a focusing device, with a cooling device being provided comprising at least one Peltier cooling element for cooling the resonator.[0004]2. The Prior Art[0005]Q-switched, pumped solid state lasers are especially ...

AI Technical Summary

Benefits of technology

[0018]It is preferably provided that the pumped light source is formed by pump diodes. Pump diodes have the advantage of a higher efficiency in comparison with flash lamps.

[0021]At least one of the cooling systems can also be used for heating the pump diodes. It is especially advantageous when during cold starting the pump diodes can be heated to operating temperature by the Peltier cooling element.

[0027]High-performance laser diodes consist of an array of numerous individual diodes and thus achieve a very high pulse energy. The laser beam can be focused only very badly as a result of the large emission surface and the non-continuous distribution (low quality). The long resonator ensures that a substantially higher beam quality and thus a smaller focus diameter can be achieved with a solid state laser.

[0029]For amplification and coherence of the light, the laser crystal is embedded in an optical resonator whose quality is increased in a pulsed manner with the Q-switch upon reaching the desired power density. A short, high laser pulse is thus obtained at the output mirror. A passive Q-switch is used, which on the one hand allows high amplification and on the other hand short energy pulses without any complex control unit.

[0032]In order to enable a very compact configuration of the ignition device, it is provided for within the scope of the invention that several pump diodes are arranged concentrically about the laser crystal. Preferably at least three and more preferably at least six pump diodes are arranged evenly about the laser crystal. The pump diodes are advantageously switched in series. The laser crystal is thus laterally pumped by the pump diodes, i.e. in a radial manner. For the purpose of increasing the pulse energy, it is also possible to arrange several rings of pump diodes in a concentric successive manner about the laser crystal.

Problems solved by technology

Actively switchable Q-switches come with the disadvantage however that a considerably complex circuitry is required for the control and that they are less suitable for rapid sequences of pulses.

In combination with the active Q-switch and the pumped light source formed by the flash lamp, the most serious disadvantage is that the device cannot be housed entirely in a component to be screwed into a spark plug shaft.

This known ignition device comes with the disadvantage of a very high constructional complexity and requires a lot of overall space in order to be used instead of a spark plug in an internal combustion engine.

Although the need for compact laser ignition devices has existed for a long time, there have not been any concrete constructional proposals for compact laser ignition devices for internal combustion engines.

Components such as cooling devices which usually require a lot of overall space are missing, which is why these systems are not yet suitable for practical use in internal combustion engines.

In the case of solid state lasers pumped with pump diodes, the problem occurs that the pump diodes can only be operated within a very narrow temperature band.

Excessive temperatures would drastically reduce the service life of the pump diodes.

Cooling alone by Peltier elements is not sufficient for the use as an ignition device in internal combustion engines.

Furthermore, the cooling is subject to further difficulties by the demand that the laser ignition device should be constructed in the highest compact manner and should be housed in the spar plug dome of a cylinder head of an internal combustion engine.

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